Advanced

On the two forms of amylose-lipid complexes

Tufvesson, Fredrik LU (2001)
Abstract (Swedish)
Popular Abstract in Swedish

Amylos-lipid-komplex är ett fenomen som förekommer i vardagliga livsmedel som innehåller stärkelse, t ex bröd och pasta. Dess struktur på molekylnivå kan liknas vid en "fransk hot dog"; franskbrödet motsvarar stärkelsemolekylen "amylos", som bildar en spiral. I dess tunnel stoppas en fet korv, vilken motsvarar en molekyl som har en lång, fet "svans". Molekylerna sitter således ihop i ett "komplex". I yttre änden kan "korven" ha ett "huvud" som gillar vatten. Så är fallet med fettsyra, som har en så kallad karboxylgrupp; och om det på huvudet sitter en glycerolgrupp, så kallas molekylen "monoglycerid". Sådana ämnen kallas "polära lipider"; de är delvis vattenlösliga och delvis fettlösliga. De... (More)
Popular Abstract in Swedish

Amylos-lipid-komplex är ett fenomen som förekommer i vardagliga livsmedel som innehåller stärkelse, t ex bröd och pasta. Dess struktur på molekylnivå kan liknas vid en "fransk hot dog"; franskbrödet motsvarar stärkelsemolekylen "amylos", som bildar en spiral. I dess tunnel stoppas en fet korv, vilken motsvarar en molekyl som har en lång, fet "svans". Molekylerna sitter således ihop i ett "komplex". I yttre änden kan "korven" ha ett "huvud" som gillar vatten. Så är fallet med fettsyra, som har en så kallad karboxylgrupp; och om det på huvudet sitter en glycerolgrupp, så kallas molekylen "monoglycerid". Sådana ämnen kallas "polära lipider"; de är delvis vattenlösliga och delvis fettlösliga. De finns naturligt i många olika livsmedelsråvaror, som t ex mjöl, ägg och mjölk.



Två olika former



Komplexen kan sedan klumpa ihop sig på olika sätt. Den ena strukturen ("form I") är relativt oordnad, medan den andra ("form II") har en tydlig kristallstruktur. Komplexform I smälter vid lägre temperatur än form II, men kan bildas snabbare. För att form II ska bildas behöver temperaturen vara minst så hög att form I börjar smälta. Även i ett riktigt livsmedel hittades form-II-komplex: i "pumpernickel-bröd", dvs bröd som hade bakats under lång tid i ugnen (20 timmar i 120°C). I vanligt bröd däremot, är komplexen i form I. Olika polära ämnen har olika lätt för att bilda komplexform II. Korta monoglycerider bildar snabbare form II jämfört med vad längre gör. Däremot bildar korta fettsyror helst inte form II, liksom inte heller laddade tensider ("diskmedelsmolekyler") gör.



Smältpunkten kan variera



Komplexens värmestabilitet beror av flera saker, och för var och en av de två komplexformerna gäller att smältpunkten: - är högre med längre polär lipid. - är lägre med mer omättad fettsyrasvans. - kan öka med hjälp av värmebehandling. - är lägre när vattenhalten är högre. När man jämför form I och form II för fettsyror och monoglycerider, så kan man se att smältpunkten för form I är högre för fettsyrakomplex jämfört med komplex med en lika lång monoglycerid, men smältpunkterna är ganska nära varandra när det gäller form II. Smältpunkten för form II är mindre beroende av egenskaperna hos den polära lipiden, jämfört med vad den är för form I.



Matsmältning



Våra enzymer i magen bryter ner stärkelsen som vi äter. Dock inte all stärkelse; en del går igenom hela tunntarmen utan att påverkas och kallas därför "resistent stärkelse". Den fungerar då som nyttiga fibrer. (Därefter kan den brytas ner av bakterier som finns i tjocktarmen.) Nedbrytningshastigheten kan minska genom tillsats av polära lipider, genom att de bildar komplex med amylos-molekyler, så att dessa går långsammare att bryta ner. Mängden resistent stärkelse kan öka under värmebehandling, genom att amylos-molekylerna kan bilda kristaller. Men om polära lipider är närvarande, så tävlar komplexbildningen med kristallbildningen, så att mängden resistent stärkelse alltså minskar.



En komplex framtid?



Idén finns att i framtiden utnyttja komplexen i pharmaceutiska beredningar eller i functional food. Bioaktiva substanser eller speciellt nyttiga ämnen (t ex fleromättade fettsyror) skulle kanske kunna bindas in i komplexen. (Less)
Abstract
This thesis is about the formation of amylose-lipid complexes, and their properties. Two forms of superstructures can be identified. Complex form I has more randomly distributed helices, while the structure of form II is crystalline and therefore exhibits the typical V-pattern in X-ray diffraction analyses. Form II has higher heat stability, and is produced by heating at a temperature at least sufficiently high to partly melt form I complexes. Complex form II was created in a gel of ordinary starch and in a real food product: "pumpernickel" bread (baked 20 h at 120°C), i.e. not only in model systems. Thus, crystallization into form II is neither prevented by the amylopectin nor the bread structure. Monoglycerides and fatty acids can create... (More)
This thesis is about the formation of amylose-lipid complexes, and their properties. Two forms of superstructures can be identified. Complex form I has more randomly distributed helices, while the structure of form II is crystalline and therefore exhibits the typical V-pattern in X-ray diffraction analyses. Form II has higher heat stability, and is produced by heating at a temperature at least sufficiently high to partly melt form I complexes. Complex form II was created in a gel of ordinary starch and in a real food product: "pumpernickel" bread (baked 20 h at 120°C), i.e. not only in model systems. Thus, crystallization into form II is neither prevented by the amylopectin nor the bread structure. Monoglycerides and fatty acids can create both complex forms, but a charged surfactant created only form I, as seen from differential scanning calorimetry. Short monoglycerides (with acyl chain length 10-12) create complex form II more easily than longer monoglycerides. This might be because the complexes are smaller and therefore more mobile for ordering into form II crystals. On the other hand, short fatty acids have lower tendency to create form II compared to longer fatty acids. For fatty acids, the cooperativity of complex dissociation is decreased with shorter chains. The heat stability of each complex form increases with chain length and decreases with unsaturation, both in the case of monoglycerides and fatty acids. Form I complexes with fatty acids are more heat stable than with the corresponding monoglycerides. The heat stability of form II is less dependent on the properties of the included lipid (i.e. chain length and polar head) compared to form I. Form II is somewhat more heat stable in the case of monoglyceride compared to corresponding fatty acid. Monoglyceride mixtures may yield complex form II with higher heat stability than expected from their components. Furthermore, both complex forms can be affected by annealing so that their heat stabilities are increased. Digestibility of starch is influenced by complex formation, amylose content and heat treatments, which was seen by using in vitro models of the human digestive tracts to measure the amount of resistant starch (RS) and the rate of enzymatic starch hydrolysis. Higher amylose content reduces digestibility. Amylose molecules may show four levels of digestibility, increasing in the following order: crystalline RS, complex form II, complex form I, non-crystalline amylose. Heat treatment may enhance amylose retrogradation (i.e. crystallization). Complex-forming polar lipids may decrease digestion rate of amylose, but they are also able to reduce the amylose retrogradation and thereby increase digestibility by forming complexes. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Biliaderis, Costas, Aristotle University, Thessaloniki, Greece
organization
publishing date
type
Thesis
publication status
published
subject
keywords
bread, enzymatic hydrolysis, resistant starch, digestibility, fatty acid, monoglyceride, polar lipid, differential scanning calorimetry, annealing, amylose-lipid complex, crystallization, Food and drink technology, Livsmedelsteknik, Biotechnology, Bioteknik
pages
54 pages
publisher
Food Technology, Lund University
defense location
sal A, Kemicentrum, Lund
defense date
2001-11-09 10:15
external identifiers
  • Other:ISRN: LUTKDH/TKL0-1040/1-54
language
English
LU publication?
yes
id
f2e86cda-9239-4d94-9e0a-11ab8f4c04fb (old id 42025)
date added to LUP
2007-10-14 16:55:21
date last changed
2016-09-19 08:45:05
@phdthesis{f2e86cda-9239-4d94-9e0a-11ab8f4c04fb,
  abstract     = {This thesis is about the formation of amylose-lipid complexes, and their properties. Two forms of superstructures can be identified. Complex form I has more randomly distributed helices, while the structure of form II is crystalline and therefore exhibits the typical V-pattern in X-ray diffraction analyses. Form II has higher heat stability, and is produced by heating at a temperature at least sufficiently high to partly melt form I complexes. Complex form II was created in a gel of ordinary starch and in a real food product: "pumpernickel" bread (baked 20 h at 120°C), i.e. not only in model systems. Thus, crystallization into form II is neither prevented by the amylopectin nor the bread structure. Monoglycerides and fatty acids can create both complex forms, but a charged surfactant created only form I, as seen from differential scanning calorimetry. Short monoglycerides (with acyl chain length 10-12) create complex form II more easily than longer monoglycerides. This might be because the complexes are smaller and therefore more mobile for ordering into form II crystals. On the other hand, short fatty acids have lower tendency to create form II compared to longer fatty acids. For fatty acids, the cooperativity of complex dissociation is decreased with shorter chains. The heat stability of each complex form increases with chain length and decreases with unsaturation, both in the case of monoglycerides and fatty acids. Form I complexes with fatty acids are more heat stable than with the corresponding monoglycerides. The heat stability of form II is less dependent on the properties of the included lipid (i.e. chain length and polar head) compared to form I. Form II is somewhat more heat stable in the case of monoglyceride compared to corresponding fatty acid. Monoglyceride mixtures may yield complex form II with higher heat stability than expected from their components. Furthermore, both complex forms can be affected by annealing so that their heat stabilities are increased. Digestibility of starch is influenced by complex formation, amylose content and heat treatments, which was seen by using in vitro models of the human digestive tracts to measure the amount of resistant starch (RS) and the rate of enzymatic starch hydrolysis. Higher amylose content reduces digestibility. Amylose molecules may show four levels of digestibility, increasing in the following order: crystalline RS, complex form II, complex form I, non-crystalline amylose. Heat treatment may enhance amylose retrogradation (i.e. crystallization). Complex-forming polar lipids may decrease digestion rate of amylose, but they are also able to reduce the amylose retrogradation and thereby increase digestibility by forming complexes.},
  author       = {Tufvesson, Fredrik},
  keyword      = {bread,enzymatic hydrolysis,resistant starch,digestibility,fatty acid,monoglyceride,polar lipid,differential scanning calorimetry,annealing,amylose-lipid complex,crystallization,Food and drink technology,Livsmedelsteknik,Biotechnology,Bioteknik},
  language     = {eng},
  pages        = {54},
  publisher    = {Food Technology, Lund University},
  school       = {Lund University},
  title        = {On the two forms of amylose-lipid complexes},
  year         = {2001},
}